1. Field of the Invention
This invention relates to a manufacturing method for an abrasive tape used when a magnetic recording medium, or the like, is polished, and more particularly to a manufacturing method for an abrasive tape for burnishing items such as floppy disks which can reduce possible resultant scratches to a minimum.
2. Description of the Prior Art
In burnishing processing for floppy disks, the floppy disk is polished by means of an abrasive tape which is produced by applying an abrasive layer containing abrasives, binders, additives, and the like, on a flexible substrate, and by drying the abrasive layer. This abrasive tape is formed into a tape or a disk, and also provided with a flexible substrate, so that it is suitable for processing of a curved surface of magnetic heads and the abrasion of flexible items such as floppy disks when compared with existing hones. In addition, this abrasive tape causes the surface to be polished to suffer from less damage, and enables the precise abrasion of the flexible items, so that this tape is indispensable for finishing abrasions.
In accordance with the tendency in recent years of magnetic recording orientating toward a high recording density, further improvements in the accuracy of the burnishing processing of floppy disks have been anticipated, and, therefore, scratches made on the surface of the magnetic layers of floppy disks during the burnishing process presented a major problem. Meanwhile, several approaches have already been put forward for preventing scratches of, or the attachment of abrasion wastes to, the surface to be polished without causing abrasive effects from being damaged when a magnetic head is finished using an abrasive tape.
One example of such approaches is disclosed in Japanese Unexamined Patent Publication No. 63(1988)-16980, wherein protuberances and recesses are evenly produced on the surface of an abrasive layer by embossing processing so that resultant abrasion wastes can be caught in the recesses, whereby it is possible to prevent scratches arising from the compressive sliding of the abrasive layer over the surface of a magnetic head to be polished, or the like. However, in the burnishing processing of items such as a floppy disk, an abrasive particle of abrasive particles on an abrasive layer which tends to cause a larger amount of particles to fly away from the abrasive layer tends to exert stronger forces on localized areas of the surface to be polished, so that the surface is scratched, thereby resulting in a quality problem. Moreover, the precision processing of a helical roller for emboss processing purposes adds to the cost of resulting products.
Another example is disclosed in Japanese Unexamined Patent Publication No. 55(1980)-117730, wherein a cleaning tape is produced by heating and pressing abrasive particles consecutively and in a stepwise fashion by means of a calender roller so that the particles can be buried in an abrasive layer. This method requires the use of an abrasive particle having a size of 0.3-5.0 micrometers. In this method, the surface of the coating film is subsequently smoothed by heating the coating film to 20-60 centigrade by the calender roller while the pressure of the calender roller is kept constant (for example, 200 kg/cm), or by gradually pressing the coating film by means of the calender roller under a pressure within a range of 200 kg/cm while the temperature is kept constant (for example, 60 centigrade), or by gradually heating and pressing the coating film under a pressure within a range of 200 kg/cm. The surface of the resultant coating film thus produced is provided with a gradually coarse or gradually smooth surface, which in turn causes a clog of the magnetic head to be easily removed, thereby leads to a scratch-free magnetic head. However, the arbitrary burying of the abrasive particles in the abrasive layer causes the locations of tip ends of the abrasive particles and the depth of the recesses in the surface of the abrasive layer to become uneven. Since a large amount of abrasion wastes is resultantly produced by the burnishing of items such as a floppy disk, in some areas of the abrasive layer abrasion wastes may not be caught between abrasive particles, and hence resulting smears on the surface of a floppy disk due to the removal of abrasion wastes will be the cause of a problem.